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mptcp: fix double-free on socket dismantle
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when MPTCP server accepts an incoming connection, it clones its listener
socket. However, the pointer to 'inet_opt' for the new socket has the same
value as the original one: as a consequence, on program exit it's possible
to observe the following splat:

  BUG: KASAN: double-free in inet_sock_destruct+0x54f/0x8b0
  Free of addr ffff888485950880 by task swapper/25/0

  CPU: 25 PID: 0 Comm: swapper/25 Kdump: loaded Not tainted 6.8.0-rc1+ torvalds#609
  Hardware name: Supermicro SYS-6027R-72RF/X9DRH-7TF/7F/iTF/iF, BIOS 3.0  07/26/2013
  Call Trace:
   <IRQ>
   dump_stack_lvl+0x32/0x50
   print_report+0xca/0x620
   kasan_report_invalid_free+0x64/0x90
   __kasan_slab_free+0x1aa/0x1f0
   kfree+0xed/0x2e0
   inet_sock_destruct+0x54f/0x8b0
   __sk_destruct+0x48/0x5b0
   rcu_do_batch+0x34e/0xd90
   rcu_core+0x559/0xac0
   __do_softirq+0x183/0x5a4
   irq_exit_rcu+0x12d/0x170
   sysvec_apic_timer_interrupt+0x6b/0x80
   </IRQ>
   <TASK>
   asm_sysvec_apic_timer_interrupt+0x16/0x20
  RIP: 0010:cpuidle_enter_state+0x175/0x300
  Code: 30 00 0f 84 1f 01 00 00 83 e8 01 83 f8 ff 75 e5 48 83 c4 18 44 89 e8 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc fb 45 85 ed <0f> 89 60 ff ff ff 48 c1 e5 06 48 c7 43 18 00 00 00 00 48 83 44 2b
  RSP: 0018:ffff888481cf7d90 EFLAGS: 00000202
  RAX: 0000000000000000 RBX: ffff88887facddc8 RCX: 0000000000000000
  RDX: 1ffff1110ff588b1 RSI: 0000000000000019 RDI: ffff88887fac4588
  RBP: 0000000000000004 R08: 0000000000000002 R09: 0000000000043080
  R10: 0009b02ea273363f R11: ffff88887fabf42b R12: ffffffff932592e0
  R13: 0000000000000004 R14: 0000000000000000 R15: 00000022c880ec80
   cpuidle_enter+0x4a/0xa0
   do_idle+0x310/0x410
   cpu_startup_entry+0x51/0x60
   start_secondary+0x211/0x270
   secondary_startup_64_no_verify+0x184/0x18b
   </TASK>

  Allocated by task 6853:
   kasan_save_stack+0x1c/0x40
   kasan_save_track+0x10/0x30
   __kasan_kmalloc+0xa6/0xb0
   __kmalloc+0x1eb/0x450
   cipso_v4_sock_setattr+0x96/0x360
   netlbl_sock_setattr+0x132/0x1f0
   selinux_netlbl_socket_post_create+0x6c/0x110
   selinux_socket_post_create+0x37b/0x7f0
   security_socket_post_create+0x63/0xb0
   __sock_create+0x305/0x450
   __sys_socket_create.part.23+0xbd/0x130
   __sys_socket+0x37/0xb0
   __x64_sys_socket+0x6f/0xb0
   do_syscall_64+0x83/0x160
   entry_SYSCALL_64_after_hwframe+0x6e/0x76

  Freed by task 6858:
   kasan_save_stack+0x1c/0x40
   kasan_save_track+0x10/0x30
   kasan_save_free_info+0x3b/0x60
   __kasan_slab_free+0x12c/0x1f0
   kfree+0xed/0x2e0
   inet_sock_destruct+0x54f/0x8b0
   __sk_destruct+0x48/0x5b0
   subflow_ulp_release+0x1f0/0x250
   tcp_cleanup_ulp+0x6e/0x110
   tcp_v4_destroy_sock+0x5a/0x3a0
   inet_csk_destroy_sock+0x135/0x390
   tcp_fin+0x416/0x5c0
   tcp_data_queue+0x1bc8/0x4310
   tcp_rcv_state_process+0x15a3/0x47b0
   tcp_v4_do_rcv+0x2c1/0x990
   tcp_v4_rcv+0x41fb/0x5ed0
   ip_protocol_deliver_rcu+0x6d/0x9f0
   ip_local_deliver_finish+0x278/0x360
   ip_local_deliver+0x182/0x2c0
   ip_rcv+0xb5/0x1c0
   __netif_receive_skb_one_core+0x16e/0x1b0
   process_backlog+0x1e3/0x650
   __napi_poll+0xa6/0x500
   net_rx_action+0x740/0xbb0
   __do_softirq+0x183/0x5a4

  The buggy address belongs to the object at ffff888485950880
   which belongs to the cache kmalloc-64 of size 64
  The buggy address is located 0 bytes inside of
   64-byte region [ffff888485950880, ffff8884859508c0)

  The buggy address belongs to the physical page:
  page:0000000056d1e95e refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888485950700 pfn:0x485950
  flags: 0x57ffffc0000800(slab|node=1|zone=2|lastcpupid=0x1fffff)
  page_type: 0xffffffff()
  raw: 0057ffffc0000800 ffff88810004c640 ffffea00121b8ac0 dead000000000006
  raw: ffff888485950700 0000000000200019 00000001ffffffff 0000000000000000
  page dumped because: kasan: bad access detected

  Memory state around the buggy address:
   ffff888485950780: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
   ffff888485950800: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
  >ffff888485950880: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                     ^
   ffff888485950900: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
   ffff888485950980: 00 00 00 00 00 01 fc fc fc fc fc fc fc fc fc fc

Something similar (a refcount underflow) happens with CALIPSO/IPv6. Fix
this by duplicating IP / IPv6 options after clone, so that
ip{,6}_sock_destruct() doesn't end up freeing the same memory area twice.

Fixes: cf7da0d ("mptcp: Create SUBFLOW socket for incoming connections")
Cc: stable@vger.kernel.org
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240223-upstream-net-20240223-misc-fixes-v1-8-162e87e48497@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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@dcaratti @kuba-moo
dcaratti authored and kuba-moo committed Feb 27, 2024
1 parent 9480f38 commit 1004868
Showing 1 changed file with 49 additions and 0 deletions.
49 changes: 49 additions & 0 deletions net/mptcp/protocol.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3178,8 +3178,50 @@ static struct ipv6_pinfo *mptcp_inet6_sk(const struct sock *sk)

return (struct ipv6_pinfo *)(((u8 *)sk) + offset);
}

static void mptcp_copy_ip6_options(struct sock *newsk, const struct sock *sk)
{
const struct ipv6_pinfo *np = inet6_sk(sk);
struct ipv6_txoptions *opt;
struct ipv6_pinfo *newnp;

newnp = inet6_sk(newsk);

rcu_read_lock();
opt = rcu_dereference(np->opt);
if (opt) {
opt = ipv6_dup_options(newsk, opt);
if (!opt)
net_warn_ratelimited("%s: Failed to copy ip6 options\n", __func__);
}
RCU_INIT_POINTER(newnp->opt, opt);
rcu_read_unlock();
}
#endif

static void mptcp_copy_ip_options(struct sock *newsk, const struct sock *sk)
{
struct ip_options_rcu *inet_opt, *newopt = NULL;
const struct inet_sock *inet = inet_sk(sk);
struct inet_sock *newinet;

newinet = inet_sk(newsk);

rcu_read_lock();
inet_opt = rcu_dereference(inet->inet_opt);
if (inet_opt) {
newopt = sock_kmalloc(newsk, sizeof(*inet_opt) +
inet_opt->opt.optlen, GFP_ATOMIC);
if (newopt)
memcpy(newopt, inet_opt, sizeof(*inet_opt) +
inet_opt->opt.optlen);
else
net_warn_ratelimited("%s: Failed to copy ip options\n", __func__);
}
RCU_INIT_POINTER(newinet->inet_opt, newopt);
rcu_read_unlock();
}

struct sock *mptcp_sk_clone_init(const struct sock *sk,
const struct mptcp_options_received *mp_opt,
struct sock *ssk,
Expand All @@ -3200,6 +3242,13 @@ struct sock *mptcp_sk_clone_init(const struct sock *sk,

__mptcp_init_sock(nsk);

#if IS_ENABLED(CONFIG_MPTCP_IPV6)
if (nsk->sk_family == AF_INET6)
mptcp_copy_ip6_options(nsk, sk);
else
#endif
mptcp_copy_ip_options(nsk, sk);

msk = mptcp_sk(nsk);
msk->local_key = subflow_req->local_key;
msk->token = subflow_req->token;
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